86 740 gle poor milage 12mpg

Discussion in 'Volvo 740' started by pepe256, Sep 16, 2005.

  1. pepe256

    pepe256 Guest

    any suggsetions this is emptying my pockets i have checked for vacumm leaks
    and none heard or seen any other things?
    pepe256, Sep 16, 2005
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  2. have similar problem with 87 740gle. it starts to cut out like it is
    starving for gas or has dirt in injectors then runs fine for a while then
    does it all over again any suggestions to help out is appericiated
    badboywithbadtoyz, Sep 16, 2005
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  3. pepe256

    pepe256 Guest

    mine was doing that when i was hitting around 55mph then i had the lines
    cleaned and a fuel filter replaced and that fixed it for me
    pepe256, Sep 16, 2005
  4. pepe256

    jch Guest

    If in addition to very high fuel consumption the tail pipe is very
    black, and smells of fuel, then you should check the oxygen sensor. If
    it has failed, the ECU will have been running the engine on a rich
    mixture, causing fuel consumption to almost double. Measure the sensor
    output voltage as a double check. Generic sensors are available. Is
    yours a 1-wire or 2-wire type of sensor ? Probably a 3-wire one. If
    you need details about generic sensors, please email me off-line at
    c.o.n.t.r.e.x AT s.h.a.w..c.a . You need to be concerned about the
    cat converter as well because it can plug eventually when the sensor is
    not working properly.

    / JCH
    jch, Sep 16, 2005
  5. pepe256

    pepe256 Guest

    it doesnt really put out black smoke i changed the muffler a week ago and
    been running it and doesnt really look black so if that isnt the problem
    any other suggestions
    pepe256, Sep 16, 2005
  6. A long shot but easy to try - our 85 765T ran very rich at high throttle,
    and with the turbo we could see black smoke as we tried to get it to boost.
    After driving on the highway the plugs were sooted up. It turned out to be a
    bad connection at the cylinder head temperature sensor, located under about
    the #3 intake manifold branch. It isn't visible, but if you stick your hand
    under there you can feel it. Try pulling the connector off (typical spring
    latch, just like the injectors) and pushing it back on. Then clean all the
    goo off your forearm.

    Michael Pardee, Sep 17, 2005
  7. pepe256

    James Sweet Guest

    Are you leaking? Is someone stealing your gas? The fuel is going somewhere,
    if it's not smoking check the catalytic converter, is it glowing after a
    drive? If so things to check would be the coolant temperature sensor that
    connects to the ECU and the AMM, either one can cause it to run rich. If
    it's running fine and the cat isn't excessively hot then I would suspect a
    leak or theft.
    James Sweet, Sep 17, 2005
  8. pepe256

    pepe256 Guest

    I do not believe that i am leaking and there is no one stealing my gas and
    im not smoking so i dont know im not smelling any leaking gas under the
    hood so could it be a temp sensor or what u were saying?
    pepe256, Sep 17, 2005
  9. mine does it when first starting engine. then after running it at higher
    speeds it idles down where it should. could it be the mass air flow
    badboywithbadtoyz, Sep 20, 2005
  10. replaced filter but still having same problem any other sugestions? also
    found clogged catylatic convertor put hole in front of it and seems to
    help some
    badboywithbadtoyz, Oct 1, 2005
  11. pepe256

    Randy G. Guest

    12 mpg means that it is getting about half what it should, which means
    that it is burning twice the fuel it should. This means that WAY too
    much fuel is in the cylinders, and you can guarantee that it is
    washing lubrication off the rings. Get this taken care of ASAP.

    A certified shop can place a bypass pipe in place of the convertor for
    testing purposes. Or you could drop the convertor and start it to see
    if it runs better- that is, assuming that it is running bad now beyond
    the bad fuel mileage.

    Replacement convertors are available for about $125 on eBay.

    BUT- if the car THINKS it is cold and not warming up it could be
    enriching the mixture. Other things could cause that as well I would

    If you followed my diatribe on the AMM problem you can see that it
    isn't always easy to find out what is wrong. Low spark voltage, bad
    AMM, bad IAC valve, carbon tracking in the distributor cap, bad
    ignition wires, bad coil, bad electronic ignition ground points, bad
    fuel pressure regulator... get the idea? Who knows what it could be?
    it took me two weeks to figure out that it was the AMM and only
    because I got another one and tried it.

    And one last factor that folks sometimes forget... does the car have a
    locking gas cap? Remember the story of the guy who was bragging about
    the mileage he was getting in his new VW, and the mileage slowly went
    up each week to about 48mpg becasue his friends were putting gas in
    his car each day? Later he was getting 12mpg when they started taking
    the gas OUT!

    __ __
    Randy & \ \/ /alerie's
    '90 245 Estate - '93 965 Estate
    "Shelby" & "Kate"
    Randy G., Oct 1, 2005
  12. I had the cat in our 85 765T replaced for less than $150 US parts and labor
    maybe ten years ago. It was at an independent shop in Phoenix a friend

    Isn't there an enormous amount of noise coming from that hole?

    Michael Pardee, Oct 1, 2005
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